Skin problems in individuals can result from a variety of causes: environmental assault (e.g., sun and wind), internal disease (e.g., diabetes, atherosclerosis) or normal aging. A number of structural and functional skin changes occur with aging. Further, because of the interrelationship between the structure and function of the skin, structural changes resulting from the aging process may also lead to concomitant functional impairment.
Age-associated changes are readily apparent in the epidermis, where there is an increased propensity for blistering and/or erosion. Microscopically, it has been observed that the epidermal basal cells of aged skin display greater variability in their size, shape and staining qualities than those obtained from more youthful skin. In addition, the moisture content of the stratum corneum is decreased, and cellular cohesion is diminished, particularly at the periphery of the corneocytes.
Clinically, the problem of rough or dry skin is a manifestation of several morphological changes, including the decreased moisture content of the stratum corneum, coupled with reduced eccrine and sebaceous gland output. As a person ages, there is a decrease in the epidermal turnover time, especially after the age of 50. Clinically, superficial wounds take more time to heal, making the elderly more prone to secondary infection following minor trauma.
As the skin ages, the dermis decreases in density and becomes relatively acellular and avascular. Throughout adult life, the total amount of collagen decreases about one percent per year. The collagen fibers thicken, becoming less soluble, have less capacity for swelling, and become more resistant to digestion by collagenase. There are also structural aberrations in the elastic fibers of the reticular dermis that contribute to skin sagging and a predisposition to injury.
The regression of the subepidermal elastic network may contribute to cutaneous laxity and the subtle wrinkled appearance prevalent on sun-protected skin of the elderly. Atrophy of the dermis and subcutaneous fat also plays an important role in the formation of wrinkles.
In addition, the dermis of elderly individuals has approximately 50% fewer mast cells than does that of a younger person. Clinically, this has cosmetic as well as physiologic implications. Cosmetically, the skin becomes pale with advancing age. Physiologically, the elderly patient is predisposed to both hyperthermia and hypothermia, following seemingly insignificant changes in ambient temperature. Basically, a smaller volume of blood can be diverted to the reduced capillary network of the papillary dermis following elevations in the body's core temperature, thereby diminishing cooling and resulting in hyperthermia.
Conversely, hypothermia results from the body's inability to efficiently divert blood from the skin to help conserve body heat when ambient temperatures decrease. This problem is compounded by the loss of insulating subcutaneous tissue that generally occurs in the elderly.
Many preparations have been developed for the purpose of treating human skin in an effort to counter the structural changes briefly described above, or merely to temporarily enhance the appearance of the skin. Many such preparations are directed toward moisturizing, thereby protecting the skin against drying. In general, numerous cosmetic preparations intended to combat aging in the skin exist on the market, and these preparations contain a wide variety of compounds, such as biological extracts, for example placental extracts, collagen, polyvitamin mixtures, and essential fatty acids.
However, due to the general ineffectiveness of these compositions, there exists a need in the art for improved compositions for making skin healthier, from both a structural and appearance standpoint. The present invention fulfills this need, while further providing other related advantages.